Electromagnetic device



G. W. ELMEN ELECTROMAGNETIC DEVICE June 1 1926.

Filed August 17, 1921 fl m Z m L M @W b m H Q QEGQR l atented dune ll, lh d time an aunt GUSTA'E W. ELMEN, 01F LEGNIA, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTEJTG COED PAINT, INCORPORATED, 0F NEW KORE, N. Y A CORPORATION @E NEW YGRK.

ELECTROMAGNETIC DEVICE.

Application filed ali ns-i it, 1921. Serial no. mails.

This invention relates to magnetic modu lators and similar electromagnetic systems where it is desired to utilize the magnetic efiect of a varying direct current uponan l3 alternating current, and its object is to improve the eficiency and reliability of such devices.

The invention provides an improved magnetic system for such electromagnetic devices to and makes use of a magnetic material characterized by high permeability and by low hysteresis losses.

Heretoitore iron and silicon steel. have been employed generally in electromagnetic de- 15 vices in order to secure high permeability at the forces produced by the current passing therethrough, while the principal possible rivals of iron, nickel and cobalt, have found but little application due to their in- W fcrior'magnetic characteristics. Witlnnickel and cobalt in this respect, stands Heuslers alloy of aluminum, manganese and copper.

it has been found that a composition of about two-thirds nickel and one-third copper when 25 tested at low'magnetizing forces, gives a permeability higher than that of iron alone.

It will be seen that with the exception of aluminum all these metals stand close together in their atomic Weights and atomic to numbers, and in this specification these five elements, manganese, iron, cobalt, nickel, and copper, having these consecutive atomic numbers, 25, 26,27, 28, 29, will be regarded as comprising the magnetic group of eleas ments.

.Thc criterion-oi high permeability is not the only one to be considered for seeking the best magnetic material for use in electromagnetic systems. If the magnetizing force 40 and the resultant flux are changed rapidl 1 then for most purposes, the material shot d exhibit a'low hysteresis loss. The development of eddy currents under these conditions may be obviatedito a considerable extent by lamination;' but the resistivity of the material is a factor that may he of importance in this connection;'the higher the resistivity the more the eddy current losses will be kept down.

The description hereinafter given is made specific to the employment in a magnetic modulator of a new magnetic material comprising elements of the magnetic group combined in suitable proportions, which when all subjected to a properiheat .treatment and as guarded against unduev stresses and other disturbing causes, develops and retains an extremely high permeability at low magnetizi'ng forces and a low hysteresis loss.

lron and nickel are fused together in an to induction furnace in the proportions of about 21%% ironand fil nickel. Good commercial grades of these metals are suitable for this purpose. The molten compos'ition is poured into a mold and cooled either in the form in. which it is ultimately to be used or in a convenient form to be worked over for that purpose. In the latter case it may be swaged, drawn, or rolled.

.VVhen desired to be laminated, some such W manner of working the material to the required form may be necessary.

While 78%% and 21%% have been men: I tioned as giving the proportion of the in- V gredients, nickel and iron, to be employed in making up the improved magnetic material, it will be understood that the proportion may'deviate considerably from these figures when nickel and iron are the only. ingredients, and that when there are other till ingredients, this proportion may not apply. Up to the present time when the only ingredients are nickel and iron, it has been found that a proportion about the same as a that named, ives the greatest permeability 86 for low'magnetizing forces. Other ingredients than nickel and iron may be employed for various purposes, not only to confer high permeability on the product,'but for other objects; for example, it may be desirable to so add vchromium for the reason that a comparatively small quantity of this element will cause a decided increase in the resist-ivity of the composition, and this high resistivity may beadesirable factor to out no down the eddy current lossesin the mag netic material. A composition of nickel .,55%, iron 3i%, and chromium 11%, has been carefully prepared, heat-treated and I tested, and has been found to give a high we.

value. of permeabilityat low magnetizing forces.

To. develop the utmost permeability inthe magnetic material the cores may hesubjected to a heat treatment, the treatment required M5 in any particular case varying somewhat as regards temperatures employed and-duration of heating and cooling. The optimum values of these variables may be readily determined in any Specific case by, ex-' periment. A' suitable heat treatment to .develop high permeability has been found to be to heat the material to a temperature that will be suitable for annealing, then to cool at an optimum rate that must be determined by experiment. After the heat treatment, the material must be guarded against any considerable strains, in other words, the heat treatment is applied to the. material in ;,a: form ready for assembly in the apparatus in which it is to be used.

, Referring to'thedrawin s:

Fig. lshows one type 0 a magnetic mod ulator'. i Figs. 2, -3 and 4 show curves useful in describing the operation thereof. 4 1 Referring to Fig. 1, 4 represents a radio frequency alternator, which 'is connected to a coil 5 located on one part of a core ,6. The current flowing through this circuit will be referred to as I and the circuit itself as 0,.

A. coil 7, which is also located on the core 6, is connected to an antenna 8 and to a coil 9 located on a magnetic co re 10 and thence to ound. The current in this circuit will be ereinafter referred to as I and the circuit itself as 0,. A coil 11 located on the core 10;. is connectedIthrough choke coils 12 and 13 to telephone transmitter 14 and bat rtery 15. The current in this circuit will be hereinafter-referred to as I and the circuit itself as 0 In the usual construction of this-ty of modulator the cores 6 and 10 are mad: of iron. i

-.Now, when the circuit C is closed, the current} jflowing through the'coil5 produces a certain-magnetizing force which produces lines of magnetic induction in said core. These linesof force, in cutting the -.;coil 7, set uptherein an electromotive force,- the .value of which will be dependent upon the v lines of magnetic'induetion flowing in the core. The current 1,, in passing through coil 9,. reduces a magnetizing force which mcauses 'nes of flux to be set .1: in the core 10. These lines of flux w' not, cause current to flow through -coil 11 when C is closed on account of the choke coils 12 and 13. The closing of (l results in send- ..aing current I through the coil 11, and this coil effects a change in the current I flowing in. the circuit "0,1 Y

' current I, 11 his shown. T eordinates of this'figure represent the permeability to the alternating current at a magnetizing force of about' :Olcg. s; units, and the abscissae represent. the, magnetizing force produced by the --=directcurrent. .-The curve A shows this relation-for-soft iron, and curve B for a nickel-iron. composition containing approximately .7 8 n1ckeland 21 iron.

' Referring to 2, the'eifect'of the direct n thealternating current I 1 With no direct current passing the soft iron.

' rather abrupt in the case of the nickel iron com sition. It is this change in permeabil ty atlow' magnetizing forces to alternating currents, which is affected by varying the direct current that is essential in the operation of the magnetic modulator. Usually suflicient direct current is employed so that the chan e will fall along the part of the curves w ere the permeability to the alternatin current decreases with an increase, in irect current. The following description will be made specific to this general practice.

' Assuming that the circuit C, no capacity therein, the inductance in the. circuit is determined by the two currents I and I, and the current in circuit C, may be readily ascertained from a curve such as that shown in F ig. 3. 'The ordinates of this curve represent the current in .circuit C and the abscissae represent the corresponding inductance values in circuit (1 Itwill be seen from this curve that anincrease in the induotance produces a decrease in the current, and a decrease in the inductance produces an increase in the current. Now the effectof interposing capacity inv circuit C is to change the simple relation between the current and the inductance to that shown by the curve in Fig. 4. This curve is obtained from the expression E=IJW 0 00 in which-' -.E=the electromotive force in C I=the current in 0 L=the inductance in C o=21r+the frequency of the current in :the resistance of C and C=the capacity of C, The assumption is made,

plotting the curve of Fig. 4, thatthe-resistance in the circuit is negligible. The curves of Figs. 3- and 4 represent the relative change ofinductance with current for a nickel-iron composition containing. approximately 78- nickel and 21 iron. 1 1

In the operation of the magnetic modulator, circuit C is tuned witha certain amount 1- of direct current flowing through circuit C3,.

. messes This circuit is tuned so that, the maximum current which can flow therethrough is'represented by the maximum point 16 in the curve of Fig. 4, the current flowing through C being constant. It will be apparent from this curve that either an increase or decrease in I, caused by the operation of the transmitter 14 will cause the inductance in C to decrease, resulting in a detuning of the circuit. V

The effectiveness of a modulator of this type is measured by the relative change in the current I, for a variation in the direct current 1 It is desirable. that a maximum change be secured in l, for a relatively small change in 1 The great advantage to be secured in utilizing the nickel-iron compositions over that obtained when iron is employed, is shown by arconsideration of Fig. 2. In the first place, the nickel-iron compositions have a much higher permeability at low magnetiz-- ing forces than iron, which fact will permit the use of a much smaller transformer core than would be required in the case of iron,

and still retain the desired permeability; or,

if desired, the core may be made of the same size as the iron core in useat the present time, and a higher inductance obtained than has been possible formerly. In the second place, a comparatively small change in the value ofthe-direct currentflowing in cir- ,cuit C, will result in an exceedingly large change in'the permeability to the alternating current 1 and this fact will permit a great saving in the energy consumed in the operation of the device. In the third place, the rate of change of permeability to the alternating current and the magnetizing force produced by the direct current is considerably greater in the case of the nickeliron compositions, and this will permit a much better control of the radio frequency current. q p I When iron is employed in the core 10, it is necessary to useextremely thin sheets in order 'to reduce the eddy current lomes therein. The extremely high specific resistance or the nickel-iron compositions, however, will Warrant the use of much thicker sheets and therefore efiect a great saving in the expense of constructing the core.

It has been found that the nickel-iron compositions possess a much smaller hysteresis loss than iron and this characteristic fur ther accentuates the advantages to be secured from theuse of the ironnickel compositions as a core material.

While one particular nickel-iron composition has been referred to as a basis of comparison with iron, it is not intended to restrict the scope of this invention to this particular composition, but it is to be'understood that all such nickel-iron compositions which exhibit; the magnetic properties herevention, it is not intended to limit the inven tion thereto. Other magnetic devices which comprise an alternating current circuit and a direct current circuit,may also be pro vided with the ma netic material of the invention with beneficial results.

"What is claimed is:

1. A magnetic circuit, 'two electric cir' cuits interlinked therewith, means to pass variable currents of high and low periodicity in said electric circuits, respectively, said magnetic circuit being of relatively high permeability at lowcmagnetizing forces whereby slight variations of the low perio-v dicity current produce large variations of the high periodicity current.

2. An electromagnetic device comprising an alternating current circuit and a direct current circuit, and having a magnetic material comprising two elements of the magnetic group.

3. An electromagnetic device comprising an alternating current circuit and a direct current circuit, and having a magnetic material comprising nickel and another member of the magnetic group.

{Lain electromagnetic device comprising .an alternating current circuit and a direct netic material comprising nickel and another element of the magnetic group, the nickel component predominating and the material having a permeability higher than that of iron at low magnetizing forces.

7. A. magnetic modulator having a magnetic. material comprising nickel and iron in which'the nickel component predominates and having a permeability higher than that of iron at low magnetizing forces of the order of a few tenths of a gauss.

8. A magnetic modulator comprising a magnetic material approximately 78% per cent nickel and 21% per cent iron. 9. The combination of an alternating current circuit, a direct current circuit and a magnetic circuit inductively related to said circuits and composed of a material containing nickel and'iron, said material being so treated that its permeability at low magnetizing forces is higher than that of iron.

10. The combination of an alternating current circuit, a direct current circuit and a circuits and composed of a material containing nickel and iron, said material at low magnetizing forces having a permeability which is higher than that of iron and which changes rapidly with small changes in the magnetizing force.

11. The combination of an alternating current circuit, a direct current circuit and a magnetic circuit inductively related to said circuits and composed of a material contain-' ing nickel'and iron, said material at low magnetizing forces having a higher permeability than iron and having the additional property of changing its permeability more rapidly than iron in response to small changes in the magnetizing force applied.

12. The method of varying the permeability of a composition comprising two elements of the magnetic group to alternating currents producing low magnetizing forces which comprise subjecting said composition to the influence of a varying direct current.

13. The method of varying the permeability of a composition comprising .nickel and another member of the magnetic group, to alternating currents producing low mag netizing forces, which comprises subjecting said composition to the influence of a varying direct current.

14. The method of varying the permeability of a nickel-iron composition to alternating currents producing low magnetizing forces, which comprises subjecting said composition to the influence of a varying direct current.

15. In a magnetic circuit subject to a composite magnetizing force from a direct current circuit, and an alternating current'circuit interlinked with said magnetic'circuit, the method of operating efficiently which consists"in creating a large magnetic flux in the magnetic circuit by means of a small direct current magnetizing force.

16'. An electromagnetic device comprising a magnetic core consisting chiefly of nickel and iron, means for subjecting said core to a direct current flux, and additional'means for superimposing an alternating current flux on said core.

17. An electromagnetic device comprising a core composed of a material having a permeability higher than that of iron at low magnetizing forces, means for subjecting said core to a constant flux, and additionalmeans for simultaneously subjecting said core to a varying flux.

18. An electromagnetic deviceucomprising a core composed of a nickel-iron alloy in which the nickel component predominates and having a permeability higher than that of iron at low magnetizing forces of the order of a few tenths of a gauss, means for subjecting said core to a constant flux, and additional means for simultaneously subjecting said core to a varying flux. 19. An electromagnetic device comprising a magnetic core consisting chiefly of nickel and iron, means .for subjecting said core to a varying magnetizing force of high frequency, and additional means for simultaneously subjecting said core to a varying magnetizing force of low frequency. L 20. An electromagnetic device having a magnetic core composed of a nickel iron alloy in which the nickel component pre dominates, and having a permeability higher than that of iron when subjected to an alternating magnetizing force of low value, said permeability changing much more rapidly than that of iron when the core is simultaneously subjected to sniall variations in a superimposed direct current magnetizing force.

In witness whereof, I hereunto subscribe my name this 10th day of August, A. D,

GUSTAF W. ELMEN. 

